Add safe_strtoint() helper

Adds a safe strtol helper function, modeled loosely after Wayland
scanner's strtouint.  This encapsulates the various quirks of strtol
behavior, and streamlines the interface to just handling base-10 numbers
with a simple true/false error indicator and a uint32_t return by
reference.

Test cases are loosely derived from an earlier patch by Imran Zaman.

Signed-off-by: Bryce Harrington <bryce@osg.samsung.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>

tests/string-test.c

@@ -0,0 +1,87 @@
+/*
+ * Copyright © 2016 Samsung Electronics Co., Ltd
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "config.h"
+
+#include <stdlib.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <assert.h>
+
+#include "shared/string-helpers.h"
+
+#include "weston-test-client-helper.h"
+
+TEST(strtol_conversions)
+{
+	bool ret;
+	int32_t val = -1;
+	char *str = NULL;
+
+	str = ""; val = -1;
+	ret = safe_strtoint(str, &val);
+	assert(ret == false);
+	assert(val == -1);
+
+	str = "."; val = -1;
+	ret = safe_strtoint(str, &val);
+	assert(ret == false);
+	assert(val == -1);
+
+	str = "42"; val = -1;
+	ret = safe_strtoint(str, &val);
+	assert(ret == true);
+	assert(val == 42);
+
+	str = "-42"; val = -1;
+	ret = safe_strtoint(str, &val);
+	assert(ret == true);
+	assert(val == -42);
+
+	str = "0042"; val = -1;
+	ret = safe_strtoint(str, &val);
+	assert(ret == true);
+	assert(val == 42);
+
+	str = "x42"; val = -1;
+	ret = safe_strtoint(str, &val);
+	assert(ret == false);
+	assert(val == -1);
+
+	str = "42x"; val = -1;
+	ret = safe_strtoint(str, &val);
+	assert(ret == false);
+	assert(val == -1);
+
+	str = "0x42424242"; val = -1;
+	ret = safe_strtoint(str, &val);
+	assert(ret == false);
+	assert(val == -1);
+
+	str = "424748364789L"; val = -1;
+	ret = safe_strtoint(str, &val);
+	assert(ret == false);
+	assert(val == -1);
+}